Incompatable version

I was designing a login page and a home page for a webpage and had completed the login. I turned my computer off and came back later i could not open my login page error read "Could not open "path" because the file is not compatable with this version of Photoshop" this file was made with this version.I have no trouble opening the other file which i made at the same time any help would be appreciated.
PS Im thinking of getting a different version and trying it .but cant understand why it would do this.

sounds as though the file corrupted itself somehow, probably in the shutdown procedure. what version of PS are you using? and is it a windoze machine?

I am using windows Xp and its photoshop 7. I did assume this was the problem and i redone it anyway thanks for the reply....